from portlandtribune.com: The Portland Water Bureau will begin adding a small portion of water
from its Columbia South Shore Well Field into the water distribution
system on Tuesday, July 30.

The blending part of a maintenance operation. It is scheduled to end on Aug. 9. 

The
operation does not mean water behind the dams in the Bull Run watershed
have fallen so low that the groundwater must be added to solve
turbidity problems. 

According to the bureau, the groundwater
supply is a complex system composed of electric pumps, chemical feed
systems, electronic controls and other equipment that must be operated
regularly to identify maintenance needs. By doing so routinely, the
bureau helps ensure the reliability of the system when needed, either in
an emergency or to meet seasonal supply demands. 

The rate of
groundwater pumping will vary throughout each day. Groundwater will be
pumped at a rate of approximately 18 million gallons per day during work
hours. No pumping will occur at night. The rate of groundwater
production may decrease toward the end of the operation. It may be
extended as necessary. 

The average contribution of groundwater
to the system will be approximately three percent or less of the total
daily water demand, the bureau says. Because of this, the bureau does
not expect there to be a large change in water quality. It takes
approximately 24 to 60 hours for the blended water to make its way
through the distribution system to homes and businesses, depending on
location and water demand.